This invention relates to a line end stage for a television receiver and, in particular, to a transformer comprising a component of this stage. A line end stage for a television receiver includes, among other components, a transistor which functions as a switch, a high voltage rectifier, and a transformer having a primary winding and a high voltage secondary winding. The line end stage produces the high voltage required to energize the picture tube.
A conventional line end stage of this type is a relatively expensive and heavy part of the receiver, whih must withstand high voltages and currents on the order of 25,000 volts and two to three amperes. It performs several functions such as controlling the line sweep coils, and generating the high voltage for the picture tube, pulses for gating purposes and the direct operating voltages. Consequently, the stage must satisfy a number of different requirements.
More specifically, the line end stage should be as small as possible, light in weight and easy to manufacture. A low internal impedance is desirable and, despite the relatively high power involved, the stage should operate over long periods without malfunctioning.
It is known that a low internal impedance can be attained by tuning the stray inductance of the high voltage winding and the effective capacitance to certain oddnumbered harmonics of the frequency of the retrace or return sweep oscillation of the line transformer. In this way, the pulse shape of the retrace pulse is broadened so as to reduce the internal impedance of the high voltage source, it being of particular advantage to tune to the ninth harmonic of the return sweep oscillation frequency. However, tuning to such a high frequency presents a number of technical problems because of the design of the line end stage, and because the effective inductances and capacitances must not exceed certain values. Maintaining these values and simultaneously meeting the other requirements is often difficult in practice.
It is an object of the present invention to provide a line end stage having a particularly simple design and which provides a fixed coupling between the primary and high voltage windings, the stray inductance of the high voltage winding being particularly low. This stage permits tuning to the desired harmonic of the frequency of the return sweep oscillation.